Neuroendocrine cells in diffuse gastric carcinomas: an ultrastructural study with immunogold labeling of chromogranin A.

Neuroendocrine differentiation is often found in gastric carcinomas, but the relevance of these cells in gastric carcinogenesis is debated. We applied immunolabeling at the electron microscopic level to study the ultrastructure of neuroendocrine cells in gastric carcinomas to ensure correct cellular classification of dedifferentiated cells. The immunogold labeling at electron microscopic level was compared with an established sensitive immunohistochemical method using light microscopy. Thirteen human gastric adenocarcinomas of the diffuse type were examined for neuroendocrine differentiation by chromogranin A (CgA) labeling at both the light and electron microscopic level. The ultrastructure of CgA-positive cells was compared with CgA-positive cells from controls. Nine of 13 tumors showed CgA-positive cells both at the light and electron microscopic level. The CgA-positive cells displayed altered ultrastructural features compared with controls. Some of the CgA-positive tumor cells had granules typical for enterochromaffin-like cells. Immunoelectron microscopy seems to provide both significant immunolabeling and sufficient ultrastructure to enhance classification of cells in neoplastic tissue.